Study to Assess Safety and Efficacy of Ambrisentan in Subjects With Pulmonary Arterial Hypertension.

Exclusion Criteria

• •PAH due to or associated with congenital heart disease, coronary artery disease, left heart disease, interstitial lung disease, chronic obstructive pulmonary disease, veno-occlusive disease, chronic thrombotic and/or embolic disease, or sleep apnea
• •Portopulmonary hypertension
• •Bosentan within four weeks prior to Screening
• •Phosphodiesterase type V inhibitor or chronic prostanoid therapy within four weeks prior to Screening
• •IV inotrope use within two weeks prior to Screening
• •ALT or AST lab value that is greater than 1.5 times the upper limit of normal
• •Pulmonary function tests not meeting pre-specified criteria
• •Contraindication to treatment with an ERA
• •History of malignancies other than basal cell carcinoma of the skin or in situ carcinoma of the cervix within the past five years
• •Females who are pregnant or breastfeeding